The present invention relates to the filtering of electronic mail.
The usage of Internet electronic mail is proliferating. Internet electronic mail is more often becoming a replacement or supplement to the telephone, facsimile, and postal mail. However, a difficulty with this media is unsolicited bulk electronic mail that is sent by xe2x80x9celectronic marketersxe2x80x9d marketing their products. To electronic marketers, the unit cost of soliciting each recipient is virtually zero, making Internet electronic mail a very attractive solicitation distribution mechanism, even if a very low percentage of the recipients respond.
The cost, however, to recipients of bulk electronic mail is substantial. Beyond consumption of Internet resources used in transmission, bulk electronic mail results in its recipients frequently finding their electronic inbox inundated with undesired electronic mail. This inundation greatly reduces the utility of the electronic mail because time is wasted in reviewing the inbox to separate the desired electronic mail from the undesired. In addition, many electronic mail users xe2x80x9cdownloadxe2x80x9d their mail to a local workstation. For these users, the download time can be significantly increased due to electronic mail they do not want to read anyway.
Various providers of electronic mail services (e.g. Internet providers) and software developers have attempted to alleviate this problem through the use of filters. Typically, these filters operate by blocking electronic mail that originates from sites or addresses identified as a source of bulk electronic mail. This approach to filtering has several serious drawbacks. First, it requires that the appropriate sites or addresses be identified and added to a filter list. Since the bulk electronic marketers want their material to reach as large an audience as possible, they quickly react to such filtering by moving to another source address or site. Second, blocking a site blocks all electronic mail from that site. For a particular recipient, some electronic mail solicitation from a blocked site may be desired.
Even more problematic is the common practice of forging the source address of bulk electronic mail so that is appears to come from legitimate sources. Such forgery makes electronic mail difficult to filter without affecting the innocent holder of the forged address. In some cases, the problem is so extreme that the users choose to filter all electronic mail except that from a selected list of originators. This measure greatly limits the flexibility of the media.
Based on the foregoing, it is clearly desirable to provide a method of filtering electronic mail that effectively filters unwanted bulk e-mail without relying exclusively upon the originator information in the electronic mail to indicate whether an electronic mail message is a xe2x80x9cbulkxe2x80x9d message.
A method and apparatus for identifying bulk electronic mail is provided. According to an aspect of the present invention, the contents of a plurality of electronic mail messages are tracked and used to determine whether a particular electronic mail message is bulk electronic mail or not bulk electronic mail. The manner in which an electronic mail message is processed depends on the type of the electronic mail message.
According to another aspect of the present invention, a message signature is generated from the contents of the electronic mail message and transmitted to a central server. The message server may have one or more signature elements. The central server generates counts of how many other signature elements of previously received signatures match signature elements of the just generated message signature. One or more of the counts are transmitted to the electronic mail server that transmitted the particular message signature. If the one or more counts meet a predetermined threshold, the electronic mail server marks the electronic mail message as bulk electronic mail.
According to another aspect of the present invention, the central server transmits the message signature of an identified bulk electronic mail message to an electronic mail server. The electronic mail server then compares this message signature with the message signature of another electronic mail message received by the electronic mail server in order to determine whether the received electronic mail message is bulk electronic mail.
Another aspect of the present invention, code or data is transmitted to an electroic mail server to alter the manner in which message signatures are generated. Furthermore, an electronic mail server generates, in addition to a message signature, a recipient signature, and transmits both to a central server. The central server maintains a count of how many unique signature elements recipient signature combinations it has received. If the count exceeds a threshold, then electronic mail messages with those signature elements are treated as bulk electronic mail messages.